淹水对两种甜樱桃砧木根系无氧呼吸酶及发酵产物的影响

以美早/东北山樱桃、美早/马哈利为试材,研究了淹水过程中两种甜樱桃砧木生长根、褐色木质根中无氧呼吸酶——丙酮酸脱羧酶(PDC)、乙醇脱氢酶(ADH)和乳酸脱氢酶(LDH)活性及褐色木质根的发酵产物——乙醛、乙醇和乳酸含量变化,结果表明:两类根系PDC、LDH活性均呈先升后降趋势,ADH活性变化在生长根中亦先升后降,而在褐色木质根中为上升趋势,三种酶活性变化幅度表现为生长根大于褐色木质根;美早/东北山樱桃两类根系中ADH和LDH活性增加幅度大于美早/马哈利,PDC则相反;两种砧木褐色木质根乙醛、乙醇含量呈升高趋势,乳酸含量先升后降;最终美早/东北山樱桃褐色木质根中乙醛含量低于美早/马哈利,乙醇含量则相反,而乳酸含量前者较早达峰值且高于后者峰值。     

淹水胁迫对不结球白菜根系生长与呼吸酶活性的影响

采用双套盆法,以不结球白菜‘新矮青’和‘新夏青2号’品种为材料,研究了不同时间(1、3、5、恢复7d后)和不同程度淹水处理(根淹、半淹)后不结球白菜根系生长及呼吸代谢的变化规律。结果显示:(1)与对照相比,淹水胁迫下,不结球白菜幼苗根系鲜重、根系长度、根系活力显著下降,且半淹处理的下降幅度大于根淹处理。(2)淹水胁迫下,乳酸脱氢酶(LDH)、乙醇脱氢酶(ADH)活性较对照显著升高,而苹果脱氢酶(MDH)、琥珀酸脱氢酶(SDH)活性显著降低,且半淹处理的降幅大于根淹,淹水5d后与淹水1d后有显著性差异。(3)淹水胁迫下,‘新矮青’乳酸发酵途径弱于‘新夏青2号’,乙醇发酵则相反,导致后者根系中乳酸积累多于前者,细胞质酸化较严重,降低了对淹水胁迫的耐性。研究表明,不结球白菜幼苗期受到淹水胁迫时,其有氧呼吸明显受阻,无氧呼吸代谢被促进,而且随着淹水时间的延长及淹水深度的加深,根系呼吸代谢受到的抑制程度越严重,最终导致根系生长受到抑制。     

外源亚精胺对低氧胁迫下黄瓜根系多胺含量和呼吸代谢酶活性的影响

采用营养液水培,研究了根际低氧胁迫下外源亚精胺对2个抗低氧能力不同的黄瓜品种(‘中农八号’和‘绿霸春四号’)根系中多胺含量和呼吸代谢相关酶活性的影响.结果表明,单纯低氧处理下,黄瓜幼苗根系中腐胺、亚精胺和精胺含量显著提高,异柠檬酸脱氢酶(IDH)和琥珀酸脱氢酶(SDH)活性显著降低,乳酸脱氢酶(LDH)、乙醇脱氢酶(ADH)和丙酮酸脱羧酶(PDC)活性显著提高.同时,与抗低氧能力弱的‘中农八号’相比,抗低氧能力强的‘绿霸春四号’根系LDH活性增加幅度较低,ADH活性增加幅度较高,IDH和SDH活性降幅也较小;外源亚精胺能显著提高低氧胁迫下黄瓜幼苗根系中亚精胺和精胺含量,降低腐胺含量;根系中LDH、ADH和PDC活性降低,IDH和SDH活性升高,说明黄瓜幼苗根系中较高的亚精胺、精胺含量可能有利于提高根系有氧呼吸能力,缓解低氧胁迫对植株的伤害.     

根际低氧逆境对网纹甜瓜幼苗生长及根系呼吸代谢途径的影响

以耐低氧性具有明显差异的两个网纹甜瓜(Cucumis melo var. raticulalus)品种为试材,研究了根际低氧胁迫下幼苗生长、根系活力及根系呼吸关键酶活性的变化。结果表明,根际低氧胁迫下,两品种幼苗生长均受到明显抑制,而根系活力升高;根系PDC活性两品种均显著提高,品种间无显著差异; MDH活性两品种均显著降低,且耐低氧性弱的‘西域一号’下降幅度较大;根系ADH和LDH活性两品种均显著提高,耐低氧性强的‘东方星光’ADH活性增加的幅度显著高于耐低氧性弱的‘西域一号’,而‘西域一号’LDH活性增加幅度显著高于‘东方星光’。说明‘东方星光’在低氧胁迫下能保持较高的有氧呼吸水平,无氧呼吸的主要途径为乙醇发酵,而‘西域一号’在低氧胁迫下无氧呼吸的主要途径为乳酸发酵。     

低氧胁迫对黄瓜幼苗根系无氧呼吸酶和抗氧化酶活性的影响

对两个抗低氧胁迫能力不同的黄瓜品种进行营养液水培,研究了低氧胁迫下植株根系中无氧呼吸酶和抗氧化酶活性的变化。结果表明,低氧胁迫下,黄瓜植株生长受到抑制,鲜重和干重显著降低,根系中蛋白质含量降低,而根系中乳酸脱氢酶（LDH）、丙酮酸脱羧酶（PDC）、乙醇脱氢酶（ADH）、超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性在低氧胁迫下显著提高,且提高的幅度与品种抗低氧胁迫能力的强弱有关,与“中农8号”相比,抗低氧性胁迫能力较强的“绿霸春四号”根系内LDH活性增幅较小,而ADH、PDC、SOD、POD和CAT活性增幅较大。说明较高的ADH、PDC、SOD、POD、CAT活性和较低的LDH活性有利于增强幼苗植株抗低氧胁迫的能力。     

根际低氧胁迫对网纹甜瓜生长、根呼吸代谢及抗氧化酶活性的影响

采用气雾法栽培系统,研究了根际低氧（10% O₂和5% O₂）胁迫对网纹甜瓜果实发育期间植株生长、根呼吸代谢及抗氧化酶活性的影响.结果表明：与对照相比,低氧胁迫下,网纹甜瓜株高、根长降低,植株鲜、干物质量显著下降;根呼吸速率极显著低于对照（21% O₂）,且5% O₂处理下降幅度大于10% O₂处理;乳酸脱氢酶（LDH）、乙醇脱氢酶（ADH）和丙酮酸脱羧酶（PDC）活性较对照显著升高,而苹果酸脱氢酶（MDH）活性显著降低;根系中超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性和丙二醛（MDA）含量显著高于对照,其中10% O₂处理抗氧化酶活性升高幅度显著大于5% O₂处理,而MDA含量5% O₂处理高于10% O₂处理.说明网纹甜瓜果实发育期间根际氧浓度降到10%及其以下时,根系有氧呼吸明显受阻,无氧呼吸代谢被促进,同时根系抗氧化酶发生应激反应,但随低氧胁迫时间的延长,根细胞质膜过氧化程度加剧,根系受到伤害,植株生长受到抑制,最终导致果实产量和品质下降.     

低氧胁迫下24-表油菜素内酯对黄瓜幼苗根系生长及其无氧呼吸同工酶表达的影响

采用营养液水培,研究了低氧胁迫下24-表油菜素内酯(EBR)对黄瓜幼苗根系生长及其无氧呼吸同工酶表达的影响.结果表明:低氧胁迫增强了黄瓜幼苗根系丙酮酸脱羧酶(PDC)、乙醇脱氢酶(ADH)、乳酸脱氢酶(LDH)同工酶的表达,低氧胁迫下施用外源EBR的第3天PDC、ADH同工酶的表达量分别提高了18.8％、28.8％,而第6、第9天PDC、ADH、LDH同工酶的表达减弱,比单纯低氧处理分别降低19.5％、25.6％、53.4％及26.4％、26.0％、28.4％;低氧胁迫至第9天,黄瓜幼苗根系的生长受到了显著抑制(P＜0.05),而低氧胁迫下施用EBR,黄瓜幼苗根系的生长受抑制程度减轻,其根系总长、干重、根尖数较单纯低氧处理显著增加(P＜0.05),低氧抑制了黄瓜幼苗根系的生长,低氧胁迫下营养液添加EBR可调节黄瓜根系无氧呼吸同工酶的表达,缓解低氧胁迫对黄瓜幼苗根系的伤害.     

Ca2+对低氧胁迫下黄瓜幼苗生长和根系无氧呼吸酶的影响

采用营养液水培,以抗低氧能力不同的2个黄瓜品种为试材,研究了Ca2+对黄瓜幼苗植株生长和根系无氧呼吸酶活性的影响.结果表明,在低氧胁迫下,LDH、PDC和ADH活性提高程度与幼苗的抗低氧性和Ca2+浓度密切相关.与抗低氧性较弱的"中农8号"相比,抗低氧性强的"绿霸春4号"幼苗根系LDH活性增加缓慢,而PDC和ADH活性增加幅度较大,因此增强了植株对低氧胁迫的抗性.低氧胁迫下,营养液中8 mmol·L-1 Ca2+处理能显著提高根系ADH活性,降低LDH和PDC活性,0 mmol·L-1 Ca2+处理表现出相反的规律.由此可以说明,低氧胁迫下,Ca2+能够提高ADH活性,降低LDH和PDC活性,可增强黄瓜植株对低氧胁迫的抗性.     

24-表油菜素内酯对低氧胁迫下黄瓜根系抗氧化系统及无氧呼吸酶活性的影响

用营养液水培,研究了根际低氧胁迫下24-表油菜素内酯(EBR)对2个抗低氧能力不同的黄瓜品种根系中抗氧化系统及无氧呼吸酶活性的影响。结果表明,在低氧胁迫下,EBR处理显著提高了低氧胁迫下2品种黄瓜幼苗根系SOD、POD及ADH活性,降低了O2-·、H2O2和MDA含量、LDH活性及‘中农八号’根系PDC活性,而对‘绿霸春四号’根系PDC及2个品种CAT活性无明显影响,表明外源EBR处理通过促进低氧胁迫下根系中抗氧化酶和ADH活性的提高,降低LDH活性及ROS含量,增强植株抗低氧胁迫的能力。     

D-精氨酸对低氧胁迫下黄瓜幼苗根系多胺含量和无氧呼吸代谢的影响

采用营养液水培法,研究了根际低氧胁迫下D-精氨酸（D-Arg）对两个抗低氧能力不同的黄瓜品种根系中多胺含量和无氧呼吸代谢的影响.结果表明,低氧处理下,黄瓜幼苗根系中多胺含量显著增加,无氧呼吸代谢能力提高;与抗低氧能力弱的‘中农八号’相比,抗低氧能力强的‘绿霸春四号’根系中乙醇发酵活性较高,乳酸发酵活性较低;低氧胁迫下,D-精氨酸能显著降低黄瓜幼苗根系中腐胺、亚精胺和精胺含量,根系中乙醇脱氢酶（ADH）和乳酸脱氢酶（LDH）活性增加,乙醇和乳酸含量升高,植株生长受到抑制,而外源腐胺能缓解D-精氨酸的这种作用.说明黄瓜幼苗根系中较高的多胺含量可能有利于缓解低氧胁迫对植株造成的伤害.     

长期水淹对‘中山杉118’幼苗呼吸代谢的影响

中山杉(Taxodium ‘Zhongshansha’)具有极强的耐淹性, 但其耐淹机理仍没有明确。该研究以‘中山杉118’ (Taxodium ‘Zhongshansha 118’)幼苗为对象, 在经过93天不同水淹处理(对照、水浸、浅淹、深淹)后测定中山杉叶片和根系的无氧呼吸酶活性、淀粉及可溶性糖含量、生物量以及根系活力, 从能量消耗的角度初步探索了中山杉的耐淹性。结果表明: 长期水淹使中山杉叶片与根系中3种无氧呼吸酶(乙醇脱氢酶、丙酮酸脱羧酶、乳酸脱氢酶)活性显著增加, 且叶片与根系的乙醇脱氢酶活性均高于乳酸脱氢酶活性, 中山杉的根系和叶片是通过加强以酒精发酵为主的无氧呼吸适应长期缺氧环境; 不同水淹处理的叶片中3种无氧呼吸酶活性均高于根系, 叶片对缺氧环境更加敏感; 中山杉叶片和根系淀粉、可溶性糖含量均随水淹深度的增加显著增加, 根系淀粉含量显著高于叶片, 可溶性糖含量低于叶片; 中山杉根系淀粉含量高是其能够长期忍受水淹的重要原因, 且中山杉适应长期水淹的策略为忍耐型; 经受长期水淹后中山杉根茎结合部长出气生根及茎基部膨大, 同时根系外壁的木质化能将根系与外部水淹环境隔离, 具有很强的耐淹性, 可作为湿地生态修复、消落带生物治理的优良植物材料。     

涝渍胁迫对不同树种生长和能量代谢酶活性的影响

为了解涝渍条件下不同树种的耐涝性和适应性,通过田间模拟试验,分析了涝渍胁迫对1年生落羽杉、美国山核桃和乌桕实生苗生长及能量代谢酶的影响.试验分为对照、渍水和淹水3个处理,处理时间为60 d.结果表明：在渍水和淹水条件下,3种树种的相对生长率均表现为落羽杉>美国山核桃>乌桕,落羽杉耐涝性最强,乌桕耐涝性最弱.涝渍条件下,3种树种的根冠比显著增加,更多的光合产物被分配到根系.3树种乙醇脱氢酶和乳酸脱氢酶活性显著升高,其中耐涝性强的落羽杉增加幅度不大,但一直维持在较高水平;而乌桕和美国山核桃在处理初期增幅较大,在处理后期呈下降趋势.3种树种的苹果酸脱氢酶、磷酸己糖异构酶和葡萄糖-6-磷酸脱氢酶-6-磷酸葡萄糖酸脱氢酶的活性均低于对照,其中落羽杉降幅最低,淹水条件下分别下降35.6%、21.0%和22.7%.耐涝性强的树种能够通过自身的调节,维持各种能量代谢途径的强度,为树种在低氧条件下的生命活动提供能量,进而维持一定的生长量.     

根际低氧胁迫对黄瓜幼苗根系呼吸代谢的影响

采用营养液栽培方法,研究了低氧胁迫对两个耐低氧能力不同的黄瓜品种根系呼吸代谢的影响.结果表明：低氧胁迫下,两个黄瓜品种根系三羧酸循环显著受阻,无氧呼吸代谢被促进.与耐低氧能力较弱的中农8号相比,耐低氧能力较强的绿霸春4号根系琥珀酸脱氢酶和异柠檬酸脱氢酶活性的降低幅度较小,乳酸脱氢酶活性、乳酸和丙酮酸含量的增加幅度较小,而丙酮酸脱羧酶、乙醇脱氢酶活性及乙醇、丙氨酸含量的增加幅度较大;低氧胁迫8 d时,与相应对照相比,绿霸春4号根系乙醇脱氢酶活性及乙醇和丙氨酸含量分别增加了409.30%、112.13%和30.64%,中农8号根系分别增加了110.42%、31.84%和4.78%,这是两个黄瓜品种耐低氧能力差异的主要生理原因.两品种幼苗根系丙氨酸氨基转移酶活性和乙醛含量没有显著差异.表明低氧胁迫下黄瓜根系乙醇发酵代谢途径的增强和丙氨酸的积累有利于防御低氧伤害.     

Role of antioxidant and anaerobic metabolism enzymes in providing tolerance to maize (Zea mays L.) seedlings against waterlogging

The present investigation was undertaken to identify the possible mode of mechanism that could provide tolerance to maize (Zea mays L.) seedlings under waterlogging. Using cup method, a number of maize genotypes were screened on the basis of survival of the seedlings kept under waterlogging. Two tolerant (LM5 and Parkash) and three susceptible (PMH2, JH3459 and LM14) genotypes were selected for the present study. Activities of antioxidant and ethanolic fermentation enzymes and content of hydrogen peroxide (H2O2), glutathione and ascorbic acid were determined in roots of these genotypes after 72 h of waterlogging. Waterlogging treatment caused decline in activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in all the genotypes. However, only susceptible genotypes showed slight increase in glutathione reductase (GR) activity. Significant reduction in APX/GR ratio in susceptible genotypes might be the cause of their susceptibility to waterlogging. The tolerant seedlings had higher GR activity than susceptible genotypes under unstressed conditions. Stress led to decrease in H202 and increase in glutathione content of both tolerant and susceptible genotypes, but only tolerant genotypes exhibited increase in ascorbic acid under waterlogging conditions. In the tolerant genotypes, all the enzymes of anaerobic metabolism viz. alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH) and pyruvate decarboxylase (PDC) were upregulated under waterlogging, whereas in susceptible genotypes, only ADH was upregulated, suggesting that efficient upregulation of entire anaerobic metabolic machinery is essential for providing tolerance against waterlogging. The study provides a possible mechanism for waterlogging tolerance in maize.     

Fermentation and malate metabolism in response to elevated CO2 concentrations in two strawberry cultivars

Concentrations of acetaldehyde, ethanol, ethyl acetate (EA), organic acids and activities and gene expression of alcohol dehydrogenase (ADH; EC 1.1.1.1), pyruvate decarboxylase (PDC; EC 4.1.1.1), alcohol acyltransferase (AAT; EC 1.4.1.14), malate dehydrogenase (MDH; EC 1.1.1.37), malic enzyme (ME; EC 1.1.1.40) and glutamate dehydrogenase (EC 1.4.1.14) were investigated in two strawberry ( Fragaria × ananassa Duch) cultivars with different responses to CO₂ during storage. 'Jewel' fruit treated with CO₂ accumulated acetaldehyde and ethanol but little EA, while 'Cavendish' accumulated little acetaldehyde or ethanol but accumulated EA. In CO₂-treated fruit, PDC activity was positively correlated with EA accumulation in 'Jewel' but not in 'Cavendish', while no differential effect of atmosphere was observed on its gene expression. ADH activity and gene expression show a correlation with ethanol accumulation in 'Cavendish'. In 'Jewel', there was a positive correlation between ADH gene expression and enzyme activity; however, this correlation does not explain ethanol accumulation in this cultivar. EA accumulation did not show any correlation with AAT activity and gene expression in any of the cultivars. Succinate concentrations were highest and those of malate lowest in CO₂-treated fruit of both cultivars, but MDH and ME activities were not affected by CO₂. Gene expression of MDH and ME were not affected by atmosphere in 'Cavendish', although in 'Jewel' the MDH expression was slightly lower in CO₂- than air-treated fruit. The results of this study show that differences in fermentation products and malate accumulation in CO₂-treated strawberry fruit are not consistently correlated with enzyme activities and gene expression.     

Alcohol dehydrogenase activity in the roots of marsh plants in naturally waterlogged soils

The aim of this work was to discover whether oxygen tensions in the roots of marsh plants in flooded soils are high enough to allow fully acrobic metabolism. Activity of alcohol dehydrogenase (ADH), a protein synthesised in anoxic plants, was measured in roots of marsh plants growing in habitats where the availability of oxygen to the roots would be expected to differ. Roots of Carex riparia in standing water had ADH activities about 2.5 times higher than those of phosphofructokinase, and comparable to ADH activities of Poa trivialis, Urtica dioica and Ranunculus repens roots in dry soil. Removal of the oxygen supply via aerenchyma to Carex roots caused a 30-fold increase in ADH activity relative to that of phosphofructokinase. There was no change in ADH activity with depth in Carex roots in waterlogged soil, but in Filipendula ulmaria roots activity was 14 times higher below 10 cm depth than near the surface. Urtica roots in waterlogged soil had alcohol dehydrogenase activities 26 times higher than roots in dry soil, but for Poa and Ranunculus roots this figure was only 1.7 and 4.2, respectively. These results indicate that the oxygen tensions in the roots of marsh plants in waterlogged soil differ considerably among species. Ethanol was the major product of fermentation in roots of all species studied. There was no correlation between ADH activity and the rate of ethanol production under anoxia of Urtica roots. The physiological significance of high ADH activities in roots is thus unclear.Abbreviations ADH alcohol dehydrogenase - PFK phosphofructokinase - PFP pyrophosphate:fructose 6-phosphate phosphotransferase     

Evaluation of the importance of lactate for the activation of ethanolic fermentation in lettuce roots in anoxia

According to the Davies–Roberts hypothesis, plants primarily respond to oxygen limitation by a burst of lactate production and the resulting pH drop in the cytoplasm activates ethanolic fermentation. To evaluate this system in lettuce ( Lactuca sativa L.), seedlings were subjected to anoxia and in vitro activities of alcohol dehydrogenase (ADH, EC 1.1.1.1), pyruvate decarboxylase (PDC, EC 4.1.1.1) and lactate dehydrogenase (LDH, EC 1.1.1.27) and concentrations of ethanol, acetaldehyde and lactate were determined in roots of the seedlings. The in vitro activities of ADH and PDC in the roots increase in anoxia, whereas no significant increase was measured in LDH activity. At 6 h, the ADH and PDC activities in the roots kept in anoxia were 2.8- and 2.9-fold greater than those in air, respectively. Ethanol and acetaldehyde in the roots accumulated rapidly in anoxia and increased 8- and 4-fold compared with those in air by 6 h, respectively. However, lactate concentration did not increase and an initial burst of lactate production was not found. Thus, ethanol and acetaldehyde production occurred without an increase in lactate synthesis. Treatments with antimycin A and salicylhydroxamic acid, which are respiratory inhibitors, to the lettuce seedlings in the presence of oxygen increased the concentrations of ethanol and acetaldehyde but not of lactate. These results suggest that ethanolic fermentation may be activated without preceding activation of lactate fermentation and may be not regulated by oxygen concentration directly.